//
// sdk.go
// Copyright (C) 2018 asxalex <asxalex@promote.cache-dns.local>
//
// Distributed under terms of the MIT license.
//

package openfluxv2sdk

import (
	"bytes"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"time"

	"github.com/nats-io/go-nats"
)

const (
	// defaultNatsServer the default nats server
	defaultNatsServer = "nats://127.0.0.1:4222"
	//DefaultUploadURL default upload url
	DefaultUploadURL = "http://127.0.0.1:4432/data.post"
	DefaultErrorURL  = "http://127.0.0.1:4432/service.error.post"
	basicPrefix      = "service.command."
	basicAckPrefix   = "service.commandack."
	heartbeatPrefix  = "service.heartbeat"

	ackUid = "ackuid"
	// MessageOK is "ok"
	MessageOK = "ok"

	// StateError for state error
	StateError = 1
	// StateOK for State ok
	StateOK = 0
	// ErrDataUnmarshalError error for data error
	ErrDataUnmarshalError = "data unmarshal error"
)

// Feedback is the feedback of the handler
type Feedback struct {
	State   int    // 0 for success, 1 for error
	Reason  string // the reason for the state = 0
	Message string // the message while State = 1
}

type errorUploadStruct struct {
	ServiceName string
	ErrorMsg    string
}

// PostStruct is the post struct
type PostStruct struct {
	Service     string
	Metric      interface{}
	Description string
}

/*
OpenfluxSdk the base type of the struct
*/
type OpenfluxSdk struct {
	C             chan string
	URL           string // where is the nats
	Subject       string // which subject are we interested in.
	Client        *nats.Conn
	Period        uint
	PeriodTask    func(chan string, uint)
	Handler       func([]byte, chan string) Feedback
	FeedbackAlone bool
}

/*
SetURL sets the url of the sdk
*/
func (o *OpenfluxSdk) SetURL(url string) {
	o.URL = url
}

/*
SetHandler sets the handler of the interested message
*/
func (o *OpenfluxSdk) SetHandler(h func([]byte, chan string) Feedback) {
	o.Handler = h
}

/*
SetSubject sets the subject which we interested in.
*/
func (o *OpenfluxSdk) SetSubject(subject string) {
	o.Subject = subject
}

/*
Run runs the sdk
*/
func (o *OpenfluxSdk) Run() {
	o.C = make(chan string)
	if o.Subject == "" && o.Handler != nil {
		log.Println("no subject is specified, so the handler will not be called.")
	}
	if o.URL == "" {
		o.URL = defaultNatsServer
		//log.Println("no URL specified, use", defaultNatsServer, "as default")
	}
	var err error
	o.Client, err = nats.Connect(o.URL)
	if err != nil {
		log.Fatal("failed to connect to discovery")
	}
	if o.Subject != "" {
		go doHeartBeat(o.Client, o.Subject)
		subject := basicPrefix + o.Subject
		//log.Printf("listening on %s\n", subject)
		o.Client.Subscribe(subject, func(msg *nats.Msg) {
			if !o.FeedbackAlone {
				go natsHandler(o.Client, msg, o.Handler, o.C, o.Subject)
			} else {
				go natsHandler2(o.Client, msg, o.Handler, o.C, o.Subject)
			}
		})
	}
	if o.PeriodTask != nil {
		go o.periodUpload()
	}
	for {
		time.Sleep(100 * time.Second)
	}
}

func doHeartBeat(client *nats.Conn, subject string) {
	for {
		client.Publish(heartbeatPrefix, []byte(subject))
		time.Sleep(60 * time.Second)
	}
}

/*
SetPeriod sets the periodic of the task
*/
func (o *OpenfluxSdk) SetPeriod(period uint) {
	o.Period = period
}

/*
SetPeriodicTask sets the periodic task
*/
func (o *OpenfluxSdk) SetPeriodicTask(f func(chan string, uint)) {
	o.PeriodTask = f
}

func (o *OpenfluxSdk) periodUpload() {
	defer func() {
		if err := recover(); err != nil {
			fmt.Println("panic", err, "recovered")
			var errmsg string
			var ok bool
			if errmsg, ok = err.(string); !ok {
				errmsg = "type inference error"
			}
			s := errorUploadStruct{ServiceName: o.Subject, ErrorMsg: errmsg}
			PostWithJSON(DefaultErrorURL, s)
			o.periodUpload()
		}
	}()
	if o.PeriodTask == nil {
		return
	}
	if o.Period == 0 {
		o.Period = 10
	}
	o.PeriodTask(o.C, o.Period)
}

func (o *OpenfluxSdk) SetFeedbackAlone() {
	o.FeedbackAlone = true
}

func natsHandler2(nc *nats.Conn, msg *nats.Msg, handler func([]byte, chan string) Feedback, c chan string, subject string) {
	defer func() {
		if err := recover(); err != nil {
			fmt.Println("panic nats", err, "recovered")
			var errmsg string
			var ok bool
			if errmsg, ok = err.(string); !ok {
				errmsg = "type inference error"
			}
			s := errorUploadStruct{ServiceName: subject, ErrorMsg: errmsg}
			PostWithJSON(DefaultErrorURL, s)
		}
	}()
	feedback := handler(msg.Data, c)
	content, _ := json.Marshal(feedback)
	fmt.Println("publishing to", basicPrefix+subject+"feedback", "with", string(content))
	nc.Publish(basicPrefix+subject+"feedback", content)
}

func natsHandler(nc *nats.Conn, msg *nats.Msg, handler func([]byte, chan string) Feedback, c chan string, subject string) {
	defer func() {
		if err := recover(); err != nil {
			fmt.Println("panic nats", err, "recovered")
			var errmsg string
			var ok bool
			if errmsg, ok = err.(string); !ok {
				errmsg = "type inference error"
			}
			s := errorUploadStruct{ServiceName: subject, ErrorMsg: errmsg}
			PostWithJSON(DefaultErrorURL, s)
		}
	}()
	m := make(map[string]interface{})
	err := json.Unmarshal(msg.Data, &m)
	topic := basicAckPrefix + subject
	if err == nil {
		if id, ok := m[ackUid]; ok {
			topic += "." + id.(string)
		}
	}
	nc.Publish(topic, []byte("ok"))
	feedback := handler(msg.Data, c)
	content, _ := json.Marshal(feedback)
	fmt.Println("publishing ", string(content))
	nc.Publish(msg.Reply, content)
}

/*
PostWithJSON post to the url, with the json data
*/
func PostWithJSON(url string, data interface{}) (map[string]interface{}, error) {

	//json序列化
	jsonStr, err := json.Marshal(data)
	if err != nil {
		return nil, err
	}

	req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonStr))
	// req.Header.Set("X-Custom-Header", "myvalue")
	req.Header.Set("Content-Type", "application/json")

	client := &http.Client{
		Timeout: 10 * time.Second,
	}
	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	body, _ := ioutil.ReadAll(resp.Body)

	res := make(map[string]interface{})
	json.Unmarshal(body, &res)
	return res, nil
}

var MbTable = []uint16{
	0X0000, 0XC0C1, 0XC181, 0X0140, 0XC301, 0X03C0, 0X0280, 0XC241,
	0XC601, 0X06C0, 0X0780, 0XC741, 0X0500, 0XC5C1, 0XC481, 0X0440,
	0XCC01, 0X0CC0, 0X0D80, 0XCD41, 0X0F00, 0XCFC1, 0XCE81, 0X0E40,
	0X0A00, 0XCAC1, 0XCB81, 0X0B40, 0XC901, 0X09C0, 0X0880, 0XC841,
	0XD801, 0X18C0, 0X1980, 0XD941, 0X1B00, 0XDBC1, 0XDA81, 0X1A40,
	0X1E00, 0XDEC1, 0XDF81, 0X1F40, 0XDD01, 0X1DC0, 0X1C80, 0XDC41,
	0X1400, 0XD4C1, 0XD581, 0X1540, 0XD701, 0X17C0, 0X1680, 0XD641,
	0XD201, 0X12C0, 0X1380, 0XD341, 0X1100, 0XD1C1, 0XD081, 0X1040,
	0XF001, 0X30C0, 0X3180, 0XF141, 0X3300, 0XF3C1, 0XF281, 0X3240,
	0X3600, 0XF6C1, 0XF781, 0X3740, 0XF501, 0X35C0, 0X3480, 0XF441,
	0X3C00, 0XFCC1, 0XFD81, 0X3D40, 0XFF01, 0X3FC0, 0X3E80, 0XFE41,
	0XFA01, 0X3AC0, 0X3B80, 0XFB41, 0X3900, 0XF9C1, 0XF881, 0X3840,
	0X2800, 0XE8C1, 0XE981, 0X2940, 0XEB01, 0X2BC0, 0X2A80, 0XEA41,
	0XEE01, 0X2EC0, 0X2F80, 0XEF41, 0X2D00, 0XEDC1, 0XEC81, 0X2C40,
	0XE401, 0X24C0, 0X2580, 0XE541, 0X2700, 0XE7C1, 0XE681, 0X2640,
	0X2200, 0XE2C1, 0XE381, 0X2340, 0XE101, 0X21C0, 0X2080, 0XE041,
	0XA001, 0X60C0, 0X6180, 0XA141, 0X6300, 0XA3C1, 0XA281, 0X6240,
	0X6600, 0XA6C1, 0XA781, 0X6740, 0XA501, 0X65C0, 0X6480, 0XA441,
	0X6C00, 0XACC1, 0XAD81, 0X6D40, 0XAF01, 0X6FC0, 0X6E80, 0XAE41,
	0XAA01, 0X6AC0, 0X6B80, 0XAB41, 0X6900, 0XA9C1, 0XA881, 0X6840,
	0X7800, 0XB8C1, 0XB981, 0X7940, 0XBB01, 0X7BC0, 0X7A80, 0XBA41,
	0XBE01, 0X7EC0, 0X7F80, 0XBF41, 0X7D00, 0XBDC1, 0XBC81, 0X7C40,
	0XB401, 0X74C0, 0X7580, 0XB541, 0X7700, 0XB7C1, 0XB681, 0X7640,
	0X7200, 0XB2C1, 0XB381, 0X7340, 0XB101, 0X71C0, 0X7080, 0XB041,
	0X5000, 0X90C1, 0X9181, 0X5140, 0X9301, 0X53C0, 0X5280, 0X9241,
	0X9601, 0X56C0, 0X5780, 0X9741, 0X5500, 0X95C1, 0X9481, 0X5440,
	0X9C01, 0X5CC0, 0X5D80, 0X9D41, 0X5F00, 0X9FC1, 0X9E81, 0X5E40,
	0X5A00, 0X9AC1, 0X9B81, 0X5B40, 0X9901, 0X59C0, 0X5880, 0X9841,
	0X8801, 0X48C0, 0X4980, 0X8941, 0X4B00, 0X8BC1, 0X8A81, 0X4A40,
	0X4E00, 0X8EC1, 0X8F81, 0X4F40, 0X8D01, 0X4DC0, 0X4C80, 0X8C41,
	0X4400, 0X84C1, 0X8581, 0X4540, 0X8701, 0X47C0, 0X4680, 0X8641,
	0X8201, 0X42C0, 0X4380, 0X8341, 0X4100, 0X81C1, 0X8081, 0X4040}

func CheckSumBigEndian(data []byte) uint16 {
	var crc16 uint16
	crc16 = 0xffff
	for _, v := range data {
		n := uint8(uint16(v) ^ crc16)
		crc16 >>= 8
		crc16 ^= MbTable[n]
	}
	b := make([]byte, 2)
	binary.LittleEndian.PutUint16(b, crc16)
	crc16 = binary.BigEndian.Uint16(b)
	return crc16
}
